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AO Module XC_Scale

Hello,

I have Fisher DVC2000 positioner for a failure open control valve, could configurte its input range hi=4mA, input range low=20mA. The purpose is to let 4mA=0% positon and 20mA=100% position. But this will cause DeltaV AO module at initial manual mode. Could I configurate XD_SCALE 0%=20mA, 100%=4mA to according with this application?

Thanks 

Daniel Lou

Daniel Lou

• 15 Sep 2025 1:11 PM
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8 Replies

• Trista VanDerVeeken

  

  • 15 Sep 2025 1:31 PM

  In order to configure for a fail open valve, you will want to check the "Increase to close" checkbox under IO_OPTS on the AO block. The faceplate will show 0% when fully closed, but 20 mA will be sent to the field. At 100% open, the field will receive 4 mA.

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• Matt Stoner

  

  • 15 Sep 2025 1:31 PM

  Leave the scale as you originally have but configure the AO1/IO_OPTS to have the Increase to Close option checked. If you want to have the analog output drive past 4 and 20 mA then you can set the OUT_LO_LIM and OUT_HI_LIM to values like -3 and 103 when your OUT_SCALE is set to 0 to 100. Be careful going to far with these as Digital Valve Controllers (DVC) will lose their memory if you go too far with these values and I would stay below/above -5 and 105.

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• Daniel Lou

  

  • 15 Sep 2025 1:47 PM

  In reply to Trista VanDerVeeken:

  customer want 20mA when valve is 100%, 4mA when valve is 0%. Same as a failure close valve, 4m=%, 20mA=100%. Is it possible in DeltaV?

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• Matt Stoner

  

  • 15 Sep 2025 2:13 PM

  In reply to Daniel Lou:

  20mA wouldn't be a Fail Open Valve, what isn't working for what they want when it is configured like fail close?

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• Tinh Phan

  

  • 15 Sep 2025 3:25 PM

  In reply to Daniel Lou:

  Seems like you want to use the DVC2000 as 4-20 mA range vs %. If you want to change the DVC2000 to operate at 4-20 mA, you will need to use the AMS Trex or AMS Device Manager and go to the Device setup and change the device range. Once you have change the device range and unit, you should be able to set the XD Scale to be 4-20 mA.

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• Daniel Lou

  

  • 16 Sep 2025 6:13 AM

  In reply to Matt Stoner:

  Hi Matt,
  
  DVC2000 could be configurated as not air pressure out when input is 20mA, so for a faile open valve actuator 20mA=100% position, the valve is fully open. Current issue is when DVC2000 config like this, AO module is in initial manual mode and could not operate.
  
  Daniel

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• Daniel Lou

  

  • 16 Sep 2025 6:15 AM

  In reply to Tinh Phan:

  HI Tinh,
  
  Yes we know how to change input range in DVC2000. Actually we want XD Scale to be 20-4mA.
  
  Daniel

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• Matt Stoner

  

  • 16 Sep 2025 1:38 PM

  In reply to Daniel Lou:

  So do you have XD_SCALE EU0 set to 4mA and EU100 set to 20mA and OUT_SCALE EU0 set to 0 and EU100 set to 100%?
  
  DeltaV won't let you have EU0 be greater than EU100 and most likely the reason you are in MAN so I think you should configure this just like a Fail Close valve based on the information you have provided.
  
  You shouldn't have the output of 0% be 100% output for the valve as this would be confusing to operators, 0% should always be valve closed and 100% would be open regardless of fail position of the valve.

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